Apparatus for testing resistance



Patented Feb. 1.4, 1933 UNITED STATES PATENT OFFICE HAROLD PENDR, OP MEBION, PENNSYLVANIA, ASSIGNOR TOY NINTERNATIQNAII'.. RESISTANCE COMPANYQOF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF DELAWARE APPARATUS FOR TESTING RESISTANCE Original application led lay 28, 1925, Serial No. 33,327, and in Germany August 8, 1925. Divided and application filed August 16, 1929, Serial No. 386,385. Again divided and this application filed January 15, 1932. Serial No. 586,730.

This invention relates to apparatus for testing the resistance of resistance material, and with regard to its more specific features to an apparatus for testing the ohmic resistance of rod or fibre-like resistance elements;`

One object of the invention is to provide a testing apparatus by means of which the resistance of a resistance element can be accurately determined. Another object of the invention is to provide a testing apparatus adapted to determine quickly the electrical resistance of -an object. Another 'object of the invention is to provide a testing apparatus adapted to disclose the variati-ons of resistance per linear distance for different parts of the same object. Another object of the invention is to permit such variations to be determined quickly. Another object of the invention is-to provide a reliable testing apparatus of simple construction -dependable in use.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts as will be exemplified in the structure to be hereinafter described, and the scope of the application of in elevation, and the remainder of the testing apparatus being shown in conventional electrical diagrammatic form.

Referring now to the drawing, .a device 38, which may be made of any good insulating substance, contains two mercury contacts 39 and 40 spread'a predetermined distance apart. Across these two contacts is connected a battery 41 and a suitable resistance measuring device 42, which may be an ordinary meg- I ger. The battery 41 constitutes a source of constant voltage electricity, while the megger actually responds to variations in current flow, and this may be calibrated in terms of resistance because the circuit responds to y the law 0=E/R. The megger 42 thus gives large enough to receive freely material to be tested, such" as a rod or filament 11. In Patent No. 1,771,055 there is described a process -for producing resistance filament consisting of av continuous glassiibre coated with a baked-coating of carbonaceous substance, and the testing apparatus which is the subject of this application is specifically adapted to test such a type of resistance element. As described in said patent, the resistance element 11, comprising a long length of glass fibre coated as specified, may be continuously fed through the passages 4, 5 and 6, and the needle of the. megger 42 will show whether or not Aohmic resistance divided by linear distance is constant over different portions of the elements., as well as the absolulte value ofthe resistance at any given portion ofl the resistance element 11. The operator can readily tell Whether or not the resistance per linear distance of the rethe bores 4, 5 and 6 orany of them, owing to the fact that the cohesive force of liquid mercury is relatively high as compared with its adhesive force for most foreign substances. Included in suchsubstances which have small adhesive attraction for mercury are most insulators.

It will be noted that the resistance mate! rial 11 is shown as a straight piece of material, and that it may be readily placed in the passages 4, 5 and 6 of the device 38 and when so placed spaced portions thereof are completely covered by the liquid mercury 39 and 40. This is an important feature of the invention, for in many prior testing devices, either the material to b tested had to be bent, or mere surface contact (as distinguished from .submerged contact) relied upon. So far as certain aspects of the invention are concerned, however, any spaced fungible conductors might be substituted for the contacts 39 and 40. By fungible I means to include liquids and nely divided solids as well as plastic substances.

rIhe apparatus may also be used for testing resistance material entirely apart from the process of or apparatusfor making it.

Such testing may be very quickly performed, and the megger 42 may be calibrated to read in terms of megohms per inch, or per centimeter, or any other desired scale.

Resistance filament 11 of the type described in the aforesaid Patent No. 1,771,055 may be produced in large quantity, and is ready for incorporation in resistance units when it has been sorted, tested for uniformity and graded according to resistance value. Such sorting, testing andgrading are important steps in the operation of any plant which manufactures resistors, and with a reliable testing apparatus even non-uniform resistance material may be salvaged, as it may be cut into lengths just long enough for embodiment in completed resistors, and then sorted or binned with my testing apparatus. An important feature of Vmy apparatus is that, in

such ltesting or sorting, there are no contacts to be adjusted, and the result is not in error Lacasse these rollers grip the material 11, drawing it through the mercury 39 and 40. The operator thus has merely to watch .the megger 42 to find the resistance value thereof. In some cases, a recording instrument might be substituted for the operators eye.

It will'thus be seen that there has been provided by this invention an apparatus in which the various objects hereinabove set forth, together with many thoroughly practical advantages, are successfully achieved.

As various possible embodiments might be made of the mechanical features of the above invention, and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. Resistance measuring apparatus comprising a pair of cups, liquid in said cups, passages .extending through said cups and connecting them whereby a straight piece ofl material may be passed through the liquid being covered thereby, and an electric circuit including a resistance measuring instrument connecting said cups.

2. Resistance measuring apparatus as claimed in claim 1 in which the liquid is mercury. n

3. Resistance measuring apparatus comprising a constantvoltage source of electricity, a pair of fungible conducting. contacts, means spacing said contacts a Constant distance apart, an electrical instrument responding to variations of current, and connections making an open circuit through the foregoing, open between said contacts.

In testimony whereof, I have signed my name to this specification this 13th day of January, 1932.

HAROLD PENDER.

due to variations of pressure at the contacting point, as is the case with solid terminal testing apparatus. The contact resistance is a large factor in the total resistance of a carbon article, but by the wide area liquidv metal contact secured in my apparatus, this source of error and particularly lof variable error is largely eliminated. The operator sorting or binning the resistance material inserts the same in the passages 4, 5 and 6 and reads the results on the meg er 42.

, When the resistance material 11 is fed through the device 38 by power, it may be pushed or drawn by a pair of rollers 14 and 15. The peripheries of these feed rollers 14 and 15 are preferably covered with ayielding material such as leather 7 and 8, and 

